[unreadable] In children with acute lymphomatic leukemia (ALL) and in myelodysplastic syndrome (MDS) with older patients it is extremely important to measure the minimal residual disease (MRD) to monitor the progress of chemotherapy at early stages. Such measurements determine the prognosis, efficacy, and levels of the treatment. The normal method for detection and monitoring is through bone marrow biopsies. Unfortunately, this method, which has not changed in 40 years, requires multiple biopsies to obtain sufficient samples and these must be made at periodic intervals to monitor the treatment. The efficiency and specificity of biopsies can be improved through the use of labeled magnetic nanoparticles and "smart" magnetic collection methods. These antibody-labeled magnetic nanoparticles attach to specific cancer cells in large numbers and the cells are then collected magnetically. This magnetic biopsy technique samples more serum volume requiring fewer biopsies due to the increased efficiency and specificity for particular cell types. The method may also be used for sampling metastatic lesions and may be extended to solid tumors. Following these procedures, magnetic nanoparticles coated with anti-cancer agents may be magnetically concentrated, resulting in direct therapeutic intervention at the cancer site. [unreadable] [unreadable]